Forced conditioning (heating, cooling and/or adjustment of humidity) of air by a centrally disposed unit (“central air conditioning”) of structures, particularly habitable buildings, is well known in developed countries. In general, in such systems, air is  drawn, into a central unit, which unit incorporates various means to heat and/or cool air as it passes through said unit. After passing through the central unit, duct-works are typically used to distribute the air into individual rooms of the structure. As air enters the room from a duct it is typically passed through a louvered register to help direct it more or less uniformly, as the occupant of the room may desire, about the room or area thereof. As heated and/or cooled air enters into a room, the air already present therein is displaced and, typically, at least part of it returned, by duct-work or passage-ways in the building, to the central unit, where additional heating and/or cooling, as may be desired, may be accomplished. Typically circulation, for heating and/or cooling is controlled by thermostat and will continue until a desired temperature or humidity has been established.
In a typical air conditioning system air is filtered at the air intake of the central unit. At that location the air is also sometimes scented. Filtering and/or scenting of the air at that location does have advantages, including but not necessarily limited to: the entirety of the air can be filtered with filtering/scenting means; cleansing the air immediately before entry into the central unit helps maintain the cleanliness of, thus reduce maintenance of, the various elements of the central unit and duct-works thereafter; and/or, by design that area is made readily accessible, thereby cleaning or changing of the filter elements is relatively facile. However, filtering and/or scenting of the air at the intake to the main/central unit has certain disadvantages, including but not necessarily limited to: a filter at the intake of the main/central unit cannot remove dust, dirt and/or other contaminants that become entrained in the air during passage of the air through duct-work of the building and does not accommodate special filtering and/or scenting desires of the occupants of individual rooms. Moreover the heating  and cooling elements of the central unit tend to remove or alter scent as scented air passes across them.
It would therefore, accordingly, be desirable to have a means to be provided where air can be at least supplementally filtered and/or scented immediately entering individual rooms of a building serviced by one or more central heating and/or air conditioning systems. To this end the invention herein disclosed is directed.
Prior art discloses certain attempts to filter air as it enters individual rooms of a building. Some of these attempts have focused on providing the air duct with some sort of filter holder. Other attempts have focused on providing the individual rooms with air registers which have been specially designed to receive an air filter. These designs focus on providing modified apparatus for receiving a filter, and such apparatus must be removed or loosened to install, remove or otherwise periodically change the air filters thereof, and, the filters of these designs are not specially adapted to disperse scenting agents into the air. Whereas the invention disclosed and claimed herein is specially adapted to both filter air and impart a scent thereto, as it enters individual rooms of a building structure, and is designed to be used in conjunction with existing “tri-louvered” ceiling registers, without modification thereof, and without the necessity of removing or loosening such registers to install said article of manufacture.